The present invention relates to rolls for use in calenders and like machines.
Many types of calenders employ rolls wherein a cylindrical shell rotatably surrounds and is movable radially of an elongated carrier (for example, an elongated shaft) the end portions of which are mounted in spherical bearings of the machine frame. Reference may be had, for example, to German Offenlegungsschrift No. 31 01 115, German Pat. No. 25 07 677 and numerous U.S. patents of the assignee of the present application. A somewhat similar mounting for a carrier which is surrounded by the shell of a roll is disclosed in German Offenlegungsschrift No. 20 35 562.
In many instances, the shell must be free to perform (within limits) radial movements relative to its carrier. If the shell is to be positively driven (namely not merely in response to rotation of a companion roll or in response to reception of torque from a sheet which is being treated by the roll), the means for transmitting torque to one end portion of the shell normally comprises a driven gear which is rigidly connected to the shell and meshes with a driver gear rotatably mounted in a stationary component of the machine frame.
The aforementioned German Pat. No. 25 07 677 discloses a roll wherein the shell is movable relative to a row of hydrostatic supporting elements which are mounted on the carrier. The supporting elements are actuatable by a pressurized hydraulic fluid so as to change the curvature of the rotating shell and to thus alter the width of the nip of the external surface of the shell and the external surface or surfaces of one or more neighboring rolls. The driven gear of the means for rotating the shell is mounted in a housing pivotable about an axis which is located in a plane parallel to the plane of transverse movement of the shaft of the shell relative to its carrier. The driver gear is journalled in the frame of the machine and the driven gear is rigidly connected to one end portion of the shell.
The just described roll exhibits numerous advantages, especially if individual hydrostatic supporting elements or relatively small groups of neighboring hydrostatic supporting elements are actuatable independently of each other so as to alter the curvature of the corresponding portions of the rotating shell. At the very least, it is possible to accurately select the curvature of the shell in that plane which includes the axis of the shell and in which the axis of the shell is movable radially of the carrier. For example, such rolls can be used with advantage in calenders for the treatment of webs of paper, textile material, metallic or synthetic plastic foils and the like. Proper selection of the width of the nip or nips of the external surface of the shell and the external surface or surfaces of one or more neighboring rolls renders it possible to properly control the quality of the running web or sheet material. Similar advantages can be achieved if such rolls are used in sheet metal rolling mills, roller type transporting systems and the like. The means for actuating or operating the hydrostatic supporting elements receives signals from sensors which ensure that the configuration or curvature of the shell is changed practically instantaneously in response to detected deviation of actual curvature of the shell from a desired or optimum curvature.
It has been found that, in conventional machines, all of the above-enumerated advantages can be exhibited only by a roll whose shell is not positively driven. At the very least, the advantages are fewer and less pronounced if the shell of the roll is driven by a set of gears which are mounted in a conventional manner, for example, as disclosed in German Pat. No. 25 07 677. On the other hand, it is often desirable to positively drive the shell of a roll which is used in a calender or the like. The need for a positive drive will arise if the speed of the shell must deviate from that speed which can be imparted to the shell by a conveyor belt or by a running sheet or web of material which advances through the nip of the shell and an adjoining roll.